The drift of spray from pesticide applications can expose people, wildlife, and the environment to pesticide residues that can cause health and environmental effects and property damage.
Various alternatives have been proposed in an attempt to reduce the amount of drifting of small droplets during spraying of an aqueous pesticide solution. For example, high molecular weight water soluble polymers such as a guar gum, xanthan gum, polyacrylamide and other ethylenically unsaturated monomers have been used as drift control agents in the agricultural application. It has been generally accepted that polymers which give optimum spray drift control are either non-ionic (e.g., acrylamide homopolymer) or have relatively low anionic content (e.g. 5 to 30 wt. %) and also have relatively high intrinsic viscosity, for instance above 6 dl/g. Guar gum is the most widely used drift control agent in the current world market. Unfortunately, these polymers have various drawbacks. Their solutions tend to show irreversible lose of their utility due to the fact that high molecular weight polymers undergo mechanical degradation of the polymer chain. In addition, typically it takes a long time for the high molecular weight polymers to evenly disperse or dissolve in aqueous liquids which may lead to many large and undissolved particles that could plug the spraying nozzle. In addition, the polymer drift control agents perform only one task to control drift of small droplets during spraying.
Spray pattern plays an important role in small droplets drifting. When water is sprayed, many small liquid droplets form a mist which easily drifts away with wind. When an aqueous spraying solution containing a guar gum is sprayed, the sprayed pattern is modified so that the number of small droplets is much reduced. Reduction of the number of small droplets increases the size of the droplets when the spray volume remains the same. In fact, the size increase in a typical spraying solution containing guar gum as the drift control agent is often too much so that there are a lot of coarse droplets which tend to bounce off the plant leave and be wasted. Over the years, researchers have found out that the optimum spray pattern has a droplet size distribution between 100-400 m.
There is a need to develop a surfactant based drift control agent capable of reducing the drifting of the small spraying drops as well as enhancing the efficacy of the pesticide without excessive large number of coarse droplets during spraying. Various surfactants are well known to enhance pesticide efficacy by modifying the surface tension of water leading to increased wetting, penetration, and absorption on the surfaces of targeted species.
U.S. Pat. No. 4,770,814 disclosed an anti-misting agent using a VES pair consisting of alkyl trimethyl quaternary surfactant and a organic acid as its counterion and a organic salt with the same ion. Example 1 (sample #2) in the document disclosed a herbicide composition containing 99.4% deionized water, 0.23% cetyltrimethylammonium salicylate, 0.27 sodium salicylate, and 0.1% 2,4-D acid herbicide. This composition was shown to reduce the number of small-sized droplets relative to the sample containing only water.